The errors in tonometry arise from three principal sources. The first is entirely within the instrument, which may furnish wrong data owing to poor construction. The second involves the examiner who obtains inaccurate results from a good instrument because of faulty application or inaccurate reading. The third occurs because, although the results may be as good as possible, their quantitative interpretation is wrong owing to misconceptions of the principles involved. This paper is concerned only with the first source of tonometric errors, the apparatus itself, in its most widely used form, i. e., the Schiøtz tonometer.1
The accuracy demanded of any tonometer has two aspects. Priestley Smith2 formulated the distinction with his customary insight : 1. With what degree of accuracy can one measure the impressibility of the eye? 2. With what degree of accuracy does the impressibility indicate the intraocular pressure? The kind of accuracy with which this
SACHS E, MacCRAKEN FL. PRINCIPLES OF TONOMETER STANDARDIZATION. Arch Ophthalmol. 1943;29(5):782–792. doi:10.1001/archopht.1943.00880170102010
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